/Engine/Source/Runtime/PakFile/Public/IPlatformFilePak.h
Helper function to return Child's relative path from the mount point. Returns false if Child is not equal to MountPoint and is not a child path under MountPoint, else returns true. Edits Child only if returning true, setting it to the relative path. If child equals MountPoint, returns true and sets Child to the relative path to the MountPoint, which is "/"
static bool GetRelativePathFromMountInline ( [FString](API\Runtime\Core\Containers\FString) & Child, const [FString](API\Runtime\Core\Containers\FString) & MountPoint )